1. Field of Invention
The present invention relates to a Global Positioning System (GPS) and receiver jamming and anti-jamming simulation, and more particularly to a real time simulation method and system for jamming and anti-jamming evaluation of GPS/IMU (Inertial Measurement Unit) integrated system for a hardware-in-the-loop test on the ground.
2. Description of Related Arts
The Global Positioning System (GPS) navigation satellite system was originally designed and developed to serve military needs. The GPS signal is much less susceptible to interference than a narrow-band signal due to the fact of that the GPS C/A code and P signals are both spread-spectrum signals. However, beyond a certain interference level, any radio navigation signal can be exacerbated. The ability to tolerate significant amounts of interference and hostile jamming is currently an important consideration in the design of GPS receivers and GPS/INS integrated systems.
U.S. Pat. No. 6,127,970 entitled xe2x80x9cCoupled Real Time Emulation Method for Positioning and Location Systemxe2x80x9d which is invented by the applicant of the present invention discloses a simulation method for hardware-in-the-loop test of a GPS/IMU integrated system on the ground. There are commonly unsolved difficult problems in the ground tests and laboratory hardware-in-the-loop tests of the coupled GPS/IMU integrated system on-board a vehicle such as aircraft, ship and car under GPS jamming environment.
In the ground test, since the vehicle is stationary, the inertial sensor in the GPS/IMU navigation system can not produce dynamic electronic signals for it is a self-contained device, and the GPS receiver can not output dynamic measurements. In other words, it is unable to test the accuracy and errors of a GPS/IMU integrated system installed on-board vehicle while it is stationary. It is also unable to test the accuracy and errors of a GPS/IMU integrated system installed on-board vehicle under various jamming environments while it is stationary. If the inertial sensor, the GPS receiver, and the GPS/IMU integrated system are installed on-board a ground vehicle such as a car, the tester can still process a motion test under real jamming conditions by actually driving the ground vehicle in relatively low cost. However, if the vehicle to be test is an aircraft, the cost and labors for actual-fly test are ultimately expensive.
In order to verify the correctness of the hardware and software elements and their anti-jamming capability of a fully coupled positioning system and/or to evaluate system performance on the ground or in the laboratory, the dynamic signals from the global positioning system receiver (GPSR) corrupted by jamming signals, gyros, and accelerometers are required to excite the fully coupled positioning system. The present invention relates to a Global Positioning System (GPS) and receiver jamming and anti-jamming simulation, and more particularly to a real time simulation method and system for jamming and anti-jamming evaluation of GPS/IMU (Inertial Measurement Unit) integrated system for a hardware-in-the-loop test on the ground.
The static test of a fully coupled positioning system under various jamming environments is easy where the actual inertial sensors and global positioning system receiver can be used and jammers are presented in the scene. The fully coupled positioning system is often installed on a moving platform, so that a dynamic test of the fully coupled positioning system is required before a mission. Obviously, the static method cannot be applied to the fully coupled positioning system dynamic test where the dynamic inertial measurements and global positioning system signals corrupted by jamming signals are required. Therefore, it is necessary that the essential parts of the gyros, accelerometers, and global positioning system receiver experience jamming and a trajectory identical to the expected mission for dynamic testing of the fully coupled positioning system.
The flight test provides a real environment for the fully coupled positioning system. A set of real flight tests is costly, and often not affordable during, the development of a fully coupled positioning system to meet predefined anti-jamming performance. Also, before the flight test, the fully coupled positioning system must go through a series of official tests. Thus, a real time hardware-in-the-loop simulation of a gyro, accelerometer, and a global positioning system receiver suffering various jamming signals is necessary during the development of a fully coupled positioning system, as well as for a fully coupled positioning dynamic test before a mission.
It is an object of the present invention to provide a real time simulation method for jamming and anti-jamming evaluation of GPS systems and GPS/IMU integrated systems that renders the testing of the installed global positioning/inertial system on the vehicle can be carried out in a laboratory or in an anechoic chamber facility.
It is another object of this invention to provide a real time simulation method for jamming and anti-jamming evaluation of GPS systems and GPS/IMU integrated systems that generates dynamic gyro and accelerometer signals, and produces dynamic global positioning system receiver measurements corrupted by GPS jamming signals, under static conditions, identical to what would be encountered if the vehicle were flying. The present invention provides features supporting the development, debugging, and final integration of a GPS/IMU integrated system. It also assures testers that the global positioning/inertial integrated system on-board vehicle works properly before and during a flight test. It also helps to debug and evaluate on-board GPS/IMU integrated system under various jamming environments.
It is still another object of this invention to provide a real time simulation method for jamming and anti-jamming evaluation of GPS systems and GPS/IMU integrated systems in a real time hardware-in-the-loop static or dynamic test environment, which receives real time trajectory data from a 6DOF flight simulator and generates gyro electronic signals according to the gyro measurement model and error model, accelerometer electronic signals according to the accelerometer measurement model and error model, jamming signals according a jammer model, and dynamic global positioning system measurements according to the global positioning system model and the receiver model. The emulated dynamic electronic gyro and accelerometer signals and global positioning system receiver measurements corrupted by jamming signals are injected into the installed GPS/IMU integrated system to perform dynamic test of GPS/IMU integrated system on the ground under various jamming conditions.
It is a further object of this invention to provide a real time simulation method for jamming and anti-jamming evaluation of GPS systems and GPS/IMU integrated systems which allows unlimited dynamic test and performance evaluation of a GPS/IMU integrated system under various jamming conditions. With the gyro, accelerometer, jammer, and GPS receiver emulation method and system the testers are able to test the GPS/IMU integrated system performance over a real mission trajectory under various jamming scenarios.
It is still a further object of this invention to provide a real-time jamming and anti-jamming evaluation method and system that is efficiently utilized for ground test of installed system, laboratory hardware-in-the-loop dynamic simulation, and GPS/IMU integrated system analysis and development.
Another object of this invention is to provide a real time simulation method for jamming and anti-jamming evaluation of GPS systems and GPS/IMU integrated systems. In the simulated test, the reference trajectory is accurate and known, since it is defined by the testers, so that the high accuracy of the simulated method is very useful for the performance verification of the GPS/IMU integrated system under jamming conditions.
Another object of this invention is to provide a real time simulation method for jamming and anti-jamming evaluation of GPS systems and GPS/IMU integrated systems, which is adapted to predict and evaluate the dynamic performance of a GPS/IMU integrated system through a simulated test that can make the follow on real flight test safer and will greatly reduce the number of the real flight test. Consequently, the operation and test cost of the simulated method is low for it does not need the expensive motion device in the test system. The maintenance of the test system is simplified.